Apparatus for forming curved surfaces



(No Model.) I 2 Sheets-Sheet 1.

T. M. CLARK. APPARATUS FOR'FOBMING GURVED SURFACES.

No. 547,138. Patented Oct. 1, 1895.

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WITNESSES 704% 6156 046,.

ANDREW HGRAKAM.PHUTUUTNEWASNINGIUNAQC.

(No Model.) 2 SheetsSheet 2'.

- T. M. O-LARK.

APPARATUS FOR FORMING'GURVED SURFACES.

No. 547,138. Patented Oct. 1, 1895'.

WITNESSES AN nREW BI'RAHAM. FHUfO-LITHO.WA5KINGTON ,n C.

spherical aberration.

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THEODORE M. CLARK, OF NEWVTON, MASSACHUSETTS.

APPARATUS FOR FORMING CU RVED 8U RFACES.

SPECIFICATION forming part of Letters Patent No. 57,138, dated October1,1895.

Application filed J'nly 1394. Serial No. 516,6Z4- (No modelJ To all whomit may concern.-

Be it known that I, THEODORE M. CLARK, of Newton, in the county ofMiddlesex and State of Massachusetts, have invented certain new anduseful Improvements in Apparatus for Forming Curved Surfaces, of whichthe following is a specification.

The prime object of the present invention is to provide an apparatuswhereby a true parabolic surface can be produced on lenses for use incameras. It is well known that a paraboloidal lens possesses greatadvantages over a spherical lens by reason of its annulling Thedifficulty heretofore attending the production of paraboloidal lensesand the consequent expense has made their employment very limited.

I have devised an apparatus of comparatively simple construction whichwill accurately form paraboloidal surfaces in a thoroughly practicalmanner.

My invention is based upon the known principle that if one leg of aright angle passes through the focus of a parabola while the vertex ofthe angle moves in a line tangent to the parabola at its apex the otherleg of the right angle will always be tangent to the parabola.

In addition to the capability of the apparatus to produce paraboloidalsurfaces it may be adapted for the production of surfaces of othercontour.

An embodiment of the invention is illustrated in the accompanyingdrawings, which form part of this specification.

Figure 1 shows a perspective view ofa machine embodying the invention.Fig.2 shows a section on line 2 2 of Fig. 1. Fig. 3 shows a section online 3 3 of Fig. 1. Fig. 4 shows a top plan view of the machine.

The supporting-frame of theapparatus comprises a base a, adapted tostand on a bench or other elevated support, a pair of uprights a atopposite sides of said base, and another pair of uprights a at the othertwo opposite sides of the base. The uprights a are slotted vertically,and guide-strips b are secured at opposite sides of the slots, saidstrips being set obliquely for convenience in assembling the parts. Ablock 0 is fitted to each set of guiding-strips, and one of said stripsis marked with graduations and the adjacent edge of the block carries aVernier. The block is tapped to receive a vertical adj ustment-screwd,whose opposite ends are journaled in bearings d, fastened across theends of the slicleways formed by the strips 1). A milled head (1 on saidscrew provides means for turning the latter, and an extremely accurateand minute adjustment can be secured by the reading of the Vernier.

Each of the blocks 0 carries on its inner side a disk 0, havingtrunnions which journal in the block and in a bracket 0 fastened to theblock, and the said disk is slotted diametrically to receive the pendentarm a of a frame 6, which lies in a plane at right angles to the arms 6and carries an abrading-diskfin the same plane.

Horizontal guideways g are arranged on the inner sides of the uprights aat right angles to the vertical ways I), and pins e projecting from theends of the frame 6, enter said guideways.

The uprights a support a horizontal bar a in which a vertical spindle hfinds a bearing, and the upper end of said spindle carries a chuck it,in which is removably secured a suitable support It for the lens 2, thelatter being cemented to the support. The spindle extends down throughthe base a and the bench and through a bracket 2", fastened under thebench, and a pulleyj is affixed to the spindle to receive rotary motionfrom any suitable source. The spindle is arranged to slide vertically toaccommodate different thicknesses of lenses, and its lower end issupported on one end of a lever 70, to which a treadle (not shown) isconnected, so that-the operator can conveniently control the position ofthe lens.

The upper ends of uprights c are braced by cross-bars a The operation isas follows: The roughlyformed lens is cemented to the support 72. andthe latter fastened in the chuck, and then the spindle is set torevolving. The frame 6 is moved back and forth, and the lens raised intocontact with the grinding-disk. The horizontal guideways g control thetraverse of the frame, while the disks 0' keep the frames pivot at onecentral point, which is in a line at right angles to the guideway g. Theresult is a paraboloidal surface on the lens, the

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grinding-disk being always in a plane tangent to a parabola whosefocus-line embraces the center of oscillation of said disk.

Grinding and polishing materials of ditferent degrees of fineness aresuccessively used until the lens is completely polished.

By turning the milled heads d the blocks 0 can beset at any focusrequired, the verniers enabling the operator to read the distance fromthe tangent slideways g to about one one-thousandth of an inch.

The swinging frame is here shown as provided with a ball at and a handlem, by which to operate it.

It is evident that the invention is capable of embodiment in other formsthan that here shown.

What I claim as new is as follows:

1. In an apparatus forgrinding curved surfaces, the combination of anoscillatory holder having a sliding engagement with its pivot, andagnide-Way engaging said holder and extending tangentially with respectto a circle described by the holder in oscillation about its pivot.

2. In an apparatus for forming paraboloidal surfaces the combination ofa suitably constructed supporting frame having vertical slide-ways,slides fitting the same and carrying pivots, adjustment screwssupporting said, slides, a carrier or holder having sliding connectionwith said pivots, and horizontal guide- Ways receiving projections onthe carrier.

8. In an apparatus for forming paraboloidal surfaces the construction ofa suitably constructed supporting frame having vertical slide-ways,slides fitted to the same, adjusting screws engaging the slides, diskspivoted to said slides, a frame having pendent arms extending at rightangles to it and having a sliding engagement with said pivoted disks,horizontal slide-Ways on the supporting-frame and receiving projectionson the pivoted frame, and a vertical spindle centrally located in thesupporting-frame.

In testimony whereof I have signed my name to this specification, in thepresence of two subscribing witnesses, this 28th day of June, A. D.189%.

THEOD ORE M. CLARK.

\Vitnesses:

HORACE BROWN, FRANK PARKER DAVIS.

